In European Patent No. 0 375 708, corresponding to U.S. Pat. No. 5,129,496, an implementation of an automatic parking brake by suitable control of a braking system is discussed. To do so, if the brake pedal is depressed and the vehicle speed drops below a very low speed value, the braking pressure is locked in, i.e., maintained at a constant level or optionally increased in at least one wheel brake via the operation of pressure-generating means, by switching at least one valve in at least one wheel brake. The locked-in braking pressure is reduced again when it is recognized that the driver wishes to perform a standing start.
In German Published Patent Application No. 196 21 628, corresponding to U.S. Pat. No. 6,009,984, is discussed an automatic parking brake function (hillholder function), which is activated when the vehicle comes to a stop with the service brake engaged. The braking pressure or braking force then prevailing is maintained or increased in at least one wheel brake, irrespective of the extent to which the brake pedal is depressed, and is then reduced again when the brake pedal is released. Such a hillholder function eliminates extensive safety measures. To support standing starts, on slopes, for example, when the brake pedal and clutch pedal are pressed simultaneously, the clutch pedal takes over the activation or deactivation of the hillholder function when the brake pedal is released. Since this device takes into account only one special standing start operation in which the brake pedal and clutch pedal are pressed simultaneously at least at one point in time, not all standing start operations, e.g., a standing start on a slope or with the parking brake engaged, are optimally handled. Therefore, the device cannot be used universally.
In German Published Patent Application No. 196 25 919, corresponding to U.S. Pat. No. 6,056,373, is discussed a creep suppression in which, with a vehicle standing still and nonetheless a movement of the vehicle being recognized, an increase in the braking effect takes place independently of the driver, in particular by an increase of braking pressure via the activation of a supply pump. This design approach also includes a standing start aid in which when the accelerator pedal is pressed and a specified threshold for the delivered engine torque is exceeded, the braking pressure required to hold the vehicle is reduced. Here also, not all standing start situations may be optimally taken into account.